Logic 9 - A datum is as valuable as it has been evaluated.
The fact that things fall when you drop them was known to many generations of people but until Sir Isaac Newton evaluated it no one knew how valuable the datum (called "gravity") was. Once it was evaluated bridges and buildings could be better built and man could even figure out how to fly.
Another example - prior to Louis Pasteur if a limb was damaged then the only way to prevent it becoming infected and eventually killing the injured person was to hack it off. When Pasteur figured out that micro-organisms caused the infection and that the infection was spread by doctors with filthy hands, suddenly the value of cleanliness was realized because it could be evaluated with a datum of comparable magnitude: dirtiness spreads disease.